Skip to main content

Full text of "Treatise On Applied Analytical Chemistry(Vol-1)"

See other formats


270

2.  Determination of the Nickel.—The slightly ammoniacal liquid
from which the ferric hydroxide has been separated is treated with slight
excess (about 50 c.c. of reagent are required per o-i gram nickel) of i%
alcoholic solution of dimethylglyoxime.   The solution is heated for about
30 minutes on the water-bath and—after the completion of the precipitation
has been ascertained by pouring a fresh quantity of the reagent down the
sides of the beaker—filtered through a tared Gooch crucible, which is re-
peatedly washed with hot water, dried at 120° and weighed:   (weight of
the nickeloxime) X 0-2032 = nickel.

3.  Determination of the Zinc.—The filtrate from the nickel precipitate
is evaporated on a water-bath with nitric and sulphuric acids to eliminate
the excess of alcohol and destroy the excess of dimethylglyoxime.   The
residue is taken up in water, the solution neutralised exactly with ammonia
and treated with 8-10 drops of 2N-hydrochloric acid, and the zinc pre-
cipitated as in the gravimetric analysis of ordinary brasses.

4.  Determination of the Cobalt.—The liquid freed from zinc sulphide
is evaporated to 50-60 c.c., neutralised with ammonia and treated at 40-50°
with a current of hydrogen sulphide.    The cobalt is precipitated as sulphide,
which is converted into sulphate and the latter weighed.

Some types of argentan contain also silver (3-10% or even more). In this
case, the silver is precipitated as chloride before the copper is determined (see
Determination of Silver in Commercial Copper). The nitrate from the silver
chloride is evaporated in presence of nitric acid to expel excess of hydrochloric
acid, the residue being dissolved in water and treated subsequently as above.

Further, manganese is sometimes present. In this case, the tin, lead and
copper are determined by the methods given for complex brasses. The iron
and manganese are then precipitated with hydrogen peroxide and ammonia,
the nitrate being employed for the determination of the nickel and zinc as
already described. The iron and manganese precipitated with hydrogen, peroxide
and ammonia may be separated and determined electrolytically or volumetrically
(see Complex Brasses) ; or the ferric and manganese oxides may be weighed
together, then dissolved in hydrochloric acid, and the iron separated as basic
acetate.

As is seen from the following table (Lunge), alloys of copper, nickel and zinc
vary in composition according to their origin, purpose, etc.

TABLE   XXXV
Compositions of Argentans


	Cu
	Ni-4-Co
	Zn
	Mn
	Fe
	Pb

Argentan from Krupps-l jj '    '     "
	58-02 60-0 1
	24-91 22-69
	16-68 16-62
	—
	0-25 0-48
	o-Il 0-16

fl   ....
	61-60
	17-00
	20-94
	0-18
	o-io
	O-2O

Argentan of quality j n].'
	6578 62-09
	"'43 7-47
	22-19 29-61
	—
	0-26 0-25
	0-24 0-53

liv    ...
	70-94
	4'99
	23-63
	~~*
	0-21
	0-24

Qualities II, III and IV are used especially for sham silver ware.of the Tin, Lead, Copper and Iron.—See Gravi-